Re: [PATCH v4 00/20] change invalidatepage prototype to acceptlength

[Lukáš Czerner]

On Tue, 14 May 2013, Lukas Czerner wrote:

> Date: Tue, 14 May 2013 18:37:14 +0200
> From: Lukas Czerner <lczerner@xxxxxxxxxx>
> To: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx,
>     linux-ext4@xxxxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, hughd@xxxxxxxxxx,
>     lczerner@xxxxxxxxxx
> Subject: [PATCH v4 00/20] change invalidatepage prototype to accept length

Hi Ted,

you've mentioned that you'll carry the changed in the ext4 tree. Are
you going to take it for the next merge window ?

However I still need some review on the mm part of the series,
Andrew, Hugh, anyone ?

Thanks!
-Lukas

> 
> Hi,
> 
> This set of patches are aimed to allow truncate_inode_pages_range() handle
> ranges which are not aligned at the end of the page. Currently it will
> hit BUG_ON() when the end of the range is not aligned. Punch hole feature
> however can benefit from this ability saving file systems some work not
> forcing them to implement their own invalidate code to handle unaligned
> ranges.
> 
> In order for this to woke we need change ->invalidatepage() address space
> operation to to accept range to invalidate by adding 'length' argument in
> addition to 'offset'. This is different from my previous attempt to create
> new aop ->invalidatepage_range (http://lwn.net/Articles/514828/) which I
> reconsidered to be unnecessary.
> 
> It would be for the best if this series could go through ext4 branch since
> there are a lot of ext4 changes which are based on dev branch of ext4 
> (git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git)
> 
> For description purposes this patch set can be divided into following
> groups:
> 
> patch 0001:    Change ->invalidatepage() prototype adding 'length' argument
> 	and changing all the instances. In very simple cases file
> 	system methods are completely adapted, otherwise only
> 	prototype is changed and the rest will follow. This patch
> 	also implement the 'range' invalidation in
> 	block_invalidatepage().
> 
> patch 0002 - 0009:
> 	Make the use of new 'length' argument in the file system
> 	itself. Some file systems can take advantage of it trying
> 	to invalidate only portion of the page if possible, some
> 	can't, however none of the file systems currently attempt
> 	to truncate non page aligned ranges.
> 
> 
> patch 0010:    Teach truncate_inode_pages_range() to handle non page aligned
> 	ranges.
> 
> patch 0011 - 0020:
> 	Ext4 changes build on top of previous changes, simplifying
> 	punch hole code. Not all changes are realated specifically
> 	to invalidatepage() change, but all are related to the punch
> 	hole feature.
> 
> Even though this patch set would mainly affect functionality of the file
> file systems implementing punch hole I've tested all the following file
> system using xfstests without noticing any bugs related to this change.
> 
> ext3, ext4, xfs, btrfs, gfs2 and reiserfs
> 
> I've also tested block size < page size on ext4 with xfstests and fsx.
> 
> 
> v3 -> v4: Some minor changes based on the reviews. Added two ext4 patches
> 	  as suggested by Jan Kara.
> 
> Thanks!
> -Lukas
> 
> 
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